23 - Decapoda

Abstract

The Decapoda (Latreille) represent a very significant order that is assigned to the class Malacostraca and encompasses an immense diversity of marine, freshwater, and semi terrestrial crustaceans, with some 10,000 species having been described. The two infra orders treated in this chapter, Caridea and Astacidea, are nearly worldwide in distribution and, for purposes of this discussion, are represented by freshwater shrimps and crayfishes. These aquatic arthropods have successfully invaded a wide variety of aquatic and semi aquatic habitats, occurring as obligate cave-dwellers as stream, lake, pond, and swamp dwellers, and as primary burrowers; a few even invade saline environments. The crayfishes and one genus of shrimps (Macrobrachium), in particular, attain the greatest size among the freshwater crustaceans in North America. This chapter illustrates the ecology and distribution of shrimps and crayfishes in North American freshwaters (treatment generally restricted to the United States). Species richness and niche diversification are particularly well demonstrated in aquatic ecosystems of the southeastern United States. That these crustaceans have successfully colonized such diverse habitats is reflected in various morphological and physiological adaptations that are discussed in the chapter. Under each major section of the chapter, a discussion of shrimps appears first, followed by that of crayfishes. Where data are somewhat limited (particularly with reference to shrimps), both groups are discussed in the same section.